158 LUTHER BURBANK 



Now we know that each particle of proto- 

 plasm, the physical basis of all life, is composed 

 of atoms of carbon, hydrogen, nitrogen, and 

 oxygen in complex combinations. A single mole- 

 cule of protoplasm may contain a thousand or 

 more atoms. 



But even allowing a thousand atoms to each 

 molecule, we have ample material for the con- 

 struction of something like eight million billion 

 molecules for each one of our 8,000 groups of 

 potential plum trees. 



Obviously there is abundant opportunity for 

 the combination of such material into complex 

 groups, quite adequate to account for the differ- 

 ent qualities of our various plums be they ever 

 so divergent as to form or size or color or flavor. 



THE BUD AS A WALLED CITY 



In this expanded view, then, it is no more 

 wonderful that a pea-sized plum bud can obtain 

 within its germ plasm the potentialities of hun- 

 dreds of varieties of future plums than that a 

 city can comprise hundreds of houses, no two 

 just alike, all built of wood, brick, stone, and 

 metal in different proportions and combinations ; 

 just as the germ cells are all built of the atoms 

 of carbon, hydrogen, nitrogen, and oxygen in 

 different combinations. 



